(CNN) -- NATO officials said Monday they have sent a team to investigate an incident in central Afghanistan where troops thought they were battling militants, but instead may have exchanged gunfire with Afghan police.

The operation, which took place Sunday in Daikundi province, led to the death of three Afghan police officers and wounded three others, the International Security Assistance Force said.

NATO troops were conducting a patrol in a village when they came across nine armed people who were setting up what "appeared to be an ambush position," the force said in a statement.

The service members called in aerial support.

Later, troops determined the air strike may have been carried out against an Afghan police team, the force said.

"While we take extraordinary precaution while conducting operations to avoid friendly casualties, it appears innocent people may have been mistakenly targeted," said U.S. Army Col. Rafael Torres, the director of the force's Joint Command Combined Joint Operations Center director.